Bar code data in the form of spaced bars contrasting with the background on which they are printed, or the like, have been known for many years. Their use became more extensive when code readers or "wands" capable of reading codes with a very high information density became commercially available. The wands generally take the form of a pencil-shaped element having electrical leads extending from the top of a housing and which connect internally with an optical reading head responsive to the information encoded in the pattern. By simply drawing the wand across the surface of the label, the wand detects and decodes the information for display and/or storage.
Bar codes have been utilized on checks and documents, as well as on machinery, equipment, parts and so forth. By means of bar coding, processes of inventory control, production and assembly may be enhanced in efficiency. Also, bar coding may permit organizations to more easily route and keep track of items or articles carrying bar coded data. In order to assure some degree of resistance to damage, it is known that bar code labels may be coated with Mylar, or a thin Mylar film may be applied over the label. Labels with Mylar film, however, are not indestructible. They are subject to scratching, tearing and other forms of accidental or intentional obliteration, which may render the label useless for its intended function. Further, the Mylar film itself may impair accurate reading if the thickness of the film is greater than the depth of field of the optical reading head of the wand.
Apart from the significant possibility of accidental damage to bar code labels, there always exists the possibility of intentional damage. In this situation, a coating of Mylar film will provide little or no protection.
The prior art also includes structures for guiding a wand during movement along the pattern of bars in the accurate reading of bar code data. In general terms, prior art of this type provides such structure to overcome problems theretofore existing when reading large numbers of different types of materials, such as a long list of individual bar codes on labels positioned in adjacent arrangement on a flat sheet or substrate.
Two patents disclosing structures for this purpose are U.S. Pat. Nos. 3,839,625 to G. E. Chadima, Jr. et al. and 3,859,632 to G. Etter. These patents disclose substantially identical structure for guiding the wand. Thus, the Etter patent includes a support which may be a guide layer having a plurality of apertures with guiding edges and a second guide layer of like design over and attached along an external edge to the support. The guide layers form a template such that code data, at a predetermined location on a document precisely located between the layers, may be read. In reading, the wand is guided by the apertures and particularly the guiding edges. The patents recite that the guiding edges overcome problems resulting from a lack of scanning precision.
Another example of the prior art which may be likened to the Etter and Chadima, Jr. et al. patents is U.S. Pat. No. 3,735,350 to J. H. Lemelson. Lemelson describes apparatus for reading coded information which may be associated with printed characters and structure for guiding the reading instrument along the code. The structure may be a ridge or groove in a substrate, or a straight-edge which is manually moved to and accurately positioned at a location for reading a desired code.
The patent to S. M. F. Mak et al., U.S. Pat. No. 3,238,501, discloses a guide for a reading instrument which, like the Lemelson teaching, is manually moved to and accurately positioned at a location for reading.
Each of the Etter, Chadima, Jr. et al., Mak et al. and Lemelson patents relate to the guiding of a reading instrument in the accurate reading of coded information, but these patents all suffer from the problem and disadvantage of having no protection for the coded data on either a label or substrate, and they all require visual contact with the coded data in reading.
Accordingly, the present invention relates to the combination of a substrate containing bar coded information and a protective device which provides protection against damage when mounted over the coding and, importantly, enables an operator to correctly read the coded data without the requirement of visual contact with the data.